Protein Biochemistry Detergents

Detergents are compounds used in many research applications, including nucleic acid extraction, protein purification, microscopy, immunostaining, and immunoassays. Structurally, detergents are amphiphilic surfactant compounds with hydrophilic headgroup and a hydrophobic hydrocarbon tail. This characteristic provides detergents with useful chemical functions in solution, such as disrupting cellular lipid membranes and solubilizing proteins. One common example is sodium dodecyl sulfate (SDS), a key component of SDS-PAGE that denatures proteins also applies the overall negative charge which drives electrophoretic movement. Tween-20, a non-ionic detergent, is routinely added to immunoassay buffers to help prevent non-specific antibody binding. Cell lysing buffers for nucleic acid or protein purification utilize detergents such as Triton-X and SDS. Detergents can be broadly categorized by the charge of their hydrophilic headgroup. Ionic detergents (such as SDS, deoxycholic acid) have charged headgroups that can either be anionic or cationic. Non-ionic detergents (Tween, Triton-X, Brij) have uncharged headgroups. Zwitterionic detergents (CHAPS, CHAPSO) contain an equal amount of positive and negative charges that result in a net zero headgroup charge. Other attributes to consider for a given detergent include its critical micelle concentration (CMC), whether it is denaturing or non-denaturing, and whether it can be removed or dialyzed out of solution.